Heretofore, as integrated passive devices (IPDs), various LC composite electronic components have been proposed in which capacitors and inductors are formed using thin film processes on a semiconductor substrate Japanese Unexamined Patent Application Publication No. 6-53406.
When a capacitor is formed using a thin film process, it is easy to form a capacitor having a large capacitance due to the fact that the distance between the capacitor electrodes can be made small. However, when an inductor is formed using a thin film process, it is difficult to make the film thicknesses of inductor conductor patterns large, and therefore in particular the direct-current resistance (DCR) of the inductor is undesirably increased. Consequently, it is difficult to form an inductor having a high Q value using a thin film process, and it is difficult to form an LC resonance circuit that has low loss in a high-frequency band in an LC composite electronic component formed using a thin film process.
On the other hand, Japanese Unexamined Patent Application Publication No. 11-67587, an LC composite electronic component having a structure in which a dielectric ceramic substrate in which a capacitor is formed and a magnetic ceramic substrate in which an inductor is formed are stacked on top of one another.
When a capacitor is formed in a dielectric ceramic substrate as in Japanese Unexamined Patent Application Publication No. 11-67587, it is difficult to make the distance between the capacitor electrodes small, and therefore it is difficult to form a capacitor having a large capacitance.
Furthermore, in the case where external terminals for realizing connections to the outside are formed on the surface of the ceramic substrate, the contraction rates and contraction behaviors of the material forming the ceramic substrate and the material of terminals at the time of firing greatly differ from each other, and therefore it is difficult to obtain high adhesion strength between the ceramic substrate and the external terminals. Therefore, when the LC composite electronic component is mounted on a mounting substrate, the LC composite electronic component is liable to fall off the mounting substrate. In addition, since the adhesion strength between the ceramic substrate and the external terminals is low, microscopic gaps are liable to form along the interfaces between the ceramic substrate and the external terminals. Therefore, there is a risk of electrochemical migration occurring due moisture infiltrating from the outside into the inside of the LC composite electronic component through the gaps and of electrical shorts occurring between the conductors formed inside the ceramic substrate and between the external terminals.
An object of the present invention is to provide an LC composite electronic component that is equipped with external terminals having high reliability and that has excellent high-frequency characteristics. Another object of the present invention is to use the LC composite electronic component to provide an LC composite electronic component mounting substrate in which the reliability of connections between the LC composite electronic component and a mounting substrate is increased.